No backing down

Detroit Diesel’s Series 60 sacrifices no power in meeting 2007 emissions.

With 8 million miles of laboratory and highway testing already under its belt, the 2007 Detroit Diesel’s Series 60 is a very experienced engine. I jumped at the chance to test it out for myself on 75 miles of Michigan roads.

The test vehicle was a Freightliner Century Condo with an Eaton Ultrashift 10-speed automatic transmission and a 455-horsepower 2007 Series 60 engine. The test route included city, country, interstate and secondary highway driving. Riding along were Detroit Diesel’s Tim Tindall, 2007 S60 program director; David “Skip” Skupien, MBE 900/MBE 4000 project manager; and a technician.

We went west on I-96 to Michigan 14, continued west to U.S. 23 and south to I-94, which we took east back to Detroit. We hauled a 53-foot dry van with a gross weight just less than 80,000 pounds.

The first thing I noticed was how much I like driving around in big trucks. The second thing was that the ’07 S60 runs just like S60s I’ve driven in previous years. Driving through the city, we came to several stops and slowed for 90-degree turns, so I got a chance to “mash on it” and see right away how the ’07 S60 handled its 40-ton load in stop-and-go traffic.

Having heard dire predictions of lost power in the ’07 engines, I paid close attention to the S60’s performance to detect any sign of decreased pulling power. If the test drive had stopped right then, I’d still have known: Detroit Diesel’s 2007 Series 60 has all the pulling power of its predecessors.

Michigan holds trucks to 55 miles per hour, and on I-96 westbound the S60 reached that speed without any indication that its 455 horsepower was weaker than earlier Series 60s. Southern Michigan is mostly flat, but there were a few 3- and 4-percent grades that showed what the S60 could do with a maximum load. At 55 miles per hour, running between 1,200 and 1,250 rpm, the S60 dutifully held its speed up all the inclines except one: a mile-long, 4-percent grade near Ann Arbor, on which we slowed to 53 miles per hour, which I’d expect from any 455-horsepower engine in similar conditions.

The S60’s engine brake was phenomenal. Even with a 40-ton load on a 4-percent downgrade at highway speeds, the S60’s engine brake quickly slowed the truck below 50 mph, and I wondered how it would perform on very long, steep grades, such as Fancy Gap on I-77 at the North Carolina/Virginia border, or Monteagle on I-24 about 40 miles west of Chattanooga in Tennessee. My sense was that the S60’s engine brake would get a heavily loaded truck down one of those hills with little to no use of air brakes.

Maybe the ’07 S60’s most impressive new component is its DDEC VI electronic controls system, which automatically handles the entire regeneration procedure.

Tindall was eager to put the aftertreatment through its regeneration cycle while I was behind the wheel, so I’d see that not only is the cycle completely automatic but also mostly unnoticeable.

“We want to show that the Series 60 does all of this without the drivers even knowing about it,” Tindall says, and DD has achieved that.

While the 1,000-degree (Fahrenheit) heat does not penetrate to the outside of the canister, it can reach the truck’s exhaust discharge. When the truck is traveling at more than 30 mph, the heat dissipates sufficiently in the wind. If the truck slows to less than 30 during the active regeneration cycle, a small dash warning light appears just above and left of the steering column.

“This is just so the driver is aware that the DPF is in active regeneration, and he might have that heat coming out his exhaust pipes,” Tindall says.

At less than 5 mph, active regeneration stops and resumes only when the truck speeds up again. This feature prevents the potentially high heat created by regeneration from damaging trailers or anything else that might be close to the exhaust discharge, Tindall says. Our test truck had thousands of miles on it accumulated at city and highway speeds, and our trailer had no signs of heat damage even just behind the exhaust discharge.

Tindall’s technician started the active regeneration cycle about a third of the way through the test drive. A computer screen mounted on the dashboard showed the input and output temperatures inside the DPF. At idle the temperatures are at about 170 degrees, normal running temperatures are about 446 degrees, and during active regeneration, temperatures inside the DPF got up to about 1,100 degrees.

When we slowed to 30 mph and or came to a stop, the illuminated dash warning light indicated regeneration was in progress. But otherwise I wouldn’t have known because the process did not affect the S60’s performance.

A more comprehensive test drive including long interrupted stretches at highway speeds and seriously challenging hills will tell more. As well, the jury won’t reach accurate verdicts on any ’07 engines until they’ve been on the market for a year or so.